U.S. patent application number 10/027915 was filed with the patent office on 2003-06-26 for flexible and conformable embolic filtering devices.
Invention is credited to Boyle, William J., Huter, Benjamin C., Huter, Scott J., Papp, John E..
Application Number | 20030120303 10/027915 |
Document ID | / |
Family ID | 21840511 |
Filed Date | 2003-06-26 |
United States Patent
Application |
20030120303 |
Kind Code |
A1 |
Boyle, William J. ; et
al. |
June 26, 2003 |
Flexible and conformable embolic filtering devices
Abstract
A self-expanding cage for use in conjunction with an embolic
filtering device includes one or more circumferential members
adapted to expand from an unexpanded position to a expanded
position within the patient's body vessel. At least one proximal
strut and at least one distal strut are attached to the
circumferential member to form the basket. The circumferential
member may include a plurality of bending regions which enhance the
ability of the circumferential member to move between the
unexpanded and expanded positions. The proximal and distal struts
can be attached to one of the bending regions. When two or more
circumferential members are utilized, each member may be connected
by a connecting strut which may be connected at a bending region.
The connecting strut can be a straight segment or may have a
non-linear shape to provide additional flexibility. The expandable
cage can be mounted to a elongated member, such as a guide wire,
and can be either permanently mounted or rotatably mounted
thereto.
Inventors: |
Boyle, William J.;
(Fallbrook, CA) ; Huter, Benjamin C.; (Murrieta,
CA) ; Huter, Scott J.; (Temecula, CA) ; Papp,
John E.; (Temecula, CA) |
Correspondence
Address: |
FULWIDER PATTON LEE & UTECHT, LLP
HOWARD HUGHES CENTER
6060 CENTER DRIVE
TENTH FLOOR
LOS ANGELES
CA
90045
US
|
Family ID: |
21840511 |
Appl. No.: |
10/027915 |
Filed: |
December 21, 2001 |
Current U.S.
Class: |
606/200 |
Current CPC
Class: |
A61F 2230/0008 20130101;
A61F 2230/008 20130101; A61F 2/0108 20200501; A61F 2002/018
20130101; A61F 2230/0006 20130101 |
Class at
Publication: |
606/200 |
International
Class: |
A61M 029/00 |
Claims
What is claimed is:
1. An expandable cage for an embolic filtering device used to
capture embolic debris in a body vessel, the cage comprising: a
circumferential member adapted to move between a collapsed position
and an expanded position, the circumferential member including a
plurality of bending regions formed therein; a proximal strut
attached to the circumferential member; and a distal strut attached
to the circumferential member.
2. The cage of claim 1, wherein the proximal strut and distal strut
are attached to the circumferential member at bending regions.
3. The cage of claim 1, wherein the proximal strut has a free end
which is adapted to be rotatably mounted on an elongated
member.
4. The cage of claim 1, further including a plurality of proximal
struts attached to bending regions located on the circumferential
member.
5. The cage of claim 1, further including a plurality of distal
struts attached to bending regions located on the circumferential
member.
6. The cage of claim 1, further including a second circumferential
member attached to the first mentioned circumferential member, the
second circumferential member including a plurality of bending
regions formed therein; wherein the distal strut is attached to the
second circumferential member.
7. The cage of claim 6, wherein the proximal strut is attached to
the first circumferential member at a bending region and the distal
strut is attached to the second circumferential member at a bending
region.
8. The cage of claim 6, wherein the first and second
circumferential members are attached to each other by at least one
connecting strut.
9. The cage of claim 7, wherein the first and second
circumferential members are attached to each other by at least one
connecting strut.
10. The cage of claim 8, wherein the connecting strut is attached
at bending regions of the first and second circumferential
members.
11. The cage of claim 9, wherein the connecting strut is attached
at bending regions of the first and second circumferential
members.
12. The cage of claim 8, wherein the connecting strut is made from
a different material than the proximal strut and distal strut.
13. The cage of claim 8, wherein the connecting strut is
independently capable of expanding or contracting when subjected to
a certain amount of force.
14. The cage of claim 8, wherein the connecting strut has an
S-shape.
15. The cage of claim 14, wherein the S-shape of the connecting
strut is capable of expanding or contracting when subjected to a
certain amount of force.
16. The cage of claim 6, further including a plurality of proximal
struts attached to bending regions located on the first
circumferential member.
17. The cage of claim 16, further including a plurality of distal
struts attached to bending regions located on the second
circumferential member.
18. The cage of claim 1, wherein each bending region is located
about 180 degrees apart from the other on the circumferential
member.
19. The cage of claim 1, wherein each bending region has a
substantial U shape.
20. The cage of claim 19, wherein each U-shaped bending region is
oriented opposite each other.
21. The cage of claim 6, wherein each bending region is located
about 180 degrees apart from the other on the circumferential
member.
22. The cage of claim 6, wherein each bending region has a
substantial U shape.
23. The cage of claim 22, wherein each U-shaped bending region is
oriented opposite each other.
24. An expandable cage for an embolic filtering device used to
capture embolic debris in a body vessel, the cage comprising: a
proximal circumferential member adapted to move between a collapsed
position and an expanded position, the proximal circumferential
member including a plurality of bending regions formed therein; a
distal circumferential member adapted to move between a collapsed
position and an expanded position, the distal circumferential
member including a plurality of bending regions formed therein, the
proximal circumferential member being connected to the distal
circumferential member; a proximal strut attached to the proximal
circumferential member; and a distal strut attached to the distal
circumferential member.
25. The cage of claim 24, wherein the proximal strut and distal
strut are attached to the proximal and distal circumferential
members at bending regions.
26. The cage of claim 25, further including a plurality of proximal
struts attached to bending regions located on the proximal
circumferential member.
27. The cage of claim 26, further including a plurality of distal
struts attached to bending regions located on the distal
circumferential member.
28. The cage of claim 24, further including another circumferential
member attached to and located between the proximal circumferential
member and the distal circumferential member.
29. The cage of claim 24, wherein the proximal and distal
circumferential members are attached to each other by at least one
connecting strut.
30. The cage of claim 29, further including a plurality of
connecting struts connecting to bending regions formed on the
proximal and distal circumferential members.
31. The cage of claim 29, wherein the connecting strut is attached
at bending regions of the proximal and distal circumferential
members.
32. The cage of claim 29, wherein the connecting strut is made from
a different material than the proximal strut and distal strut.
33. The cage of claim 29, wherein the connecting strut is
independently capable of expanding or contracting when subjected to
a certain amount of force.
34. The cage of claim 29, wherein the connecting strut has an
S-shape.
35. An expandable cage for an embolic filtering device used to
capture embolic debris in a body vessel, the cage comprising: a
proximal circumferential member adapted to move between a collapsed
position and an expanded position, the proximal circumferential
member including a plurality of bending regions formed therein; a
distal circumferential member adapted to move between a collapsed
position and an expanded position, the distal circumferential
member including a plurality of bending regions formed therein, the
proximal circumferential member being connected to the distal
circumferential member; a plurality of proximal struts attached to
the proximal circumferential member; and a plurality of distal
struts attached to the distal circumferential member.
36. The cage of claim 35, wherein each of the proximal struts is
attached to a bending region on the proximal circumferential member
and each of the distal struts is attached to a bending region on
the distal circumferential member.
37. The cage of claim 35, further including another circumferential
member attached to and located between the proximal circumferential
member and the distal circumferential member.
38. The cage of claim 35, wherein the proximal and distal
circumferential members are attached to each other by at least one
connecting strut.
39. The cage of claim 35, further including a plurality of
connecting struts which connect the proximal circumferential member
to the distal circumferential member.
40. The cage of claim 39, wherein each connecting member is
attached at a bending region on each of the proximal and distal
circumferential member.
41. An embolic filtering device used to capture embolic debris in a
body vessel, comprising: a guide wire having a proximal end and a
distal end; and an expandable filter assembly mounted near the
distal end of the guide wire, the filter assembly including a
self-expanding cage having a circumferential member adapted to move
between a collapsed position and an expanded position, the
circumferential member including a plurality of bending regions
formed therein, a proximal strut attached to the circumferential
member, a distal strut attached to the circumferential member, and
filter element attached to the expandable cage.
42. The filtering device of claim 41, wherein the proximal strut
has one end rotatably mounted to the guide wire.
43. The filtering device of claim 41, wherein the proximal strut
and distal strut are attached to the circumferential member at
bending regions.
44. The cage of claim 41, further including a plurality of proximal
struts attached to bending regions located on the circumferential
member.
45. The cage of claim 44, further including a plurality of distal
struts attached to bending regions located on the circumferential
member.
46. The filtering device of claim 45, wherein the proximal strut
and distal strut are attached to the circumferential member at
bending regions.
47. An embolic filtering device used to capture embolic debris in a
body vessel, comprising: a guide wire having a proximal end and a
distal end; and an expandable filter assembly mounted near the
distal end of the guide wire, the filter assembly including a
self-expanding cage having a proximal circumferential member
adapted to move between a collapsed position and an expanded
position, the proximal circumferential member including a plurality
of bending regions formed therein, a distal circumferential member
adapted to move between a collapsed position and an expanded
position, the distal circumferential member including a plurality
of bending regions formed therein, the proximal circumferential
member being connected to the distal circumferential member, a
proximal strut attached to the proximal circumferential member, a
distal strut attached to the distal circumferential member, and
filter element attached to the expandable cage.
48. The cage of claim 47, wherein the proximal strut and distal
strut are attached to the proximal and distal circumferential
members at bending regions.
49. The cage of claim 47, further including a plurality of proximal
struts attached to bending regions located on the proximal
circumferential member.
50. The cage of claim 49, further including a plurality of distal
struts attached to bending regions located on the distal
circumferential member.
51. The cage of claim 47, further including another circumferential
member attached to and located between the proximal circumferential
member and the distal circumferential member.
52. The cage of claim 47, wherein the proximal and distal
circumferential members are attached to each other by at least one
connecting strut.
51. The cage of claim 47, further including a plurality of
connecting struts connecting to bending regions formed on the
proximal and distal circumferential members.
52. The cage of claim 51, wherein the connecting strut is attached
at bending regions of the proximal and distal circumferential
members.
53. The cage of claim 51, wherein the connecting strut is made from
a different material than the proximal strut and distal strut.
54. An embolic filtering device used to capture embolic debris in a
body vessel, comprising: a guide wire having a proximal end and a
distal end; and an expandable filter assembly mounted near the
distal end of the guide wire, the filter assembly including a
self-expanding cage having a proximal circumferential member
adapted to move between a collapsed position and an expanded
position, the proximal circumferential member including a plurality
of bending regions formed therein, a distal circumferential member
adapted to move between a collapsed position and an expanded
position, the distal circumferential member including a plurality
of bending regions formed therein, the proximal circumferential
member being connected to the distal circumferential member, a
plurality of proximal struts attached to the proximal
circumferential member, a plurality of distal struts attached to
the distal circumferential member, and filter element attached to
the expandable cage.
55. The cage of claim 54, wherein each of the proximal struts is
attached to a bending region on the proximal circumferential member
and each of the distal struts is attached to a bending region on
the distal circumferential member.
56. The cage of claim 54, further including another circumferential
member attached to and located between the proximal circumferential
member and the distal circumferential member.
57. The cage of claim 54, wherein the proximal and distal
circumferential members are attached to each other by at least one
connecting strut.
58. The cage of claim 54, further including a plurality of
connecting struts which connect the proximal circumferential member
to the distal circumferential member.
59. The cage of claim 58, wherein each connecting member is
attached at a bending region on each of the proximal and distal
circumferential member.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to filtering devices
used when an interventional procedure is being performed in a
stenosed or occluded region of a body vessel to capture embolic
material that may be created and released into the vessel during
the procedure. The present invention is more particularly directed
to an embolic filtering device made with an expandable cage
possessing good flexibility and bendability, which allows the
embolic filtering device to be readily deployed in a bend in a body
lumen of a patient.
BACKGROUND OF THE INVENTION
[0002] Numerous procedures have been developed for treating
occluded blood vessels to allow blood to flow without obstruction.
Such procedures usually involve the percutaneous introduction of an
interventional device into the lumen of the artery, usually by a
catheter. One widely known and medically accepted procedure is
balloon angioplasty in which an inflatable balloon is introduced
within the stenosed region of the blood vessel to dilate the
occluded vessel. The balloon dilatation catheter is initially
inserted into the patient's arterial system and is advanced and
manipulated into the area of stenosis in the artery. The balloon is
inflated to compress the plaque and press the vessel wall radially
outward to increase the diameter of the blood vessel, resulting in
increased blood flow. The balloon is then deflated to a small
profile so that the dilatation catheter can be withdrawn from the
patient's vasculature and the blood flow resumed through the
dilated artery. As should be appreciated by those skilled in the
art, while the above-described procedure is typical, it is not the
only method used in angioplasty.
[0003] Another procedure is laser angioplasty which utilizes a
laser to ablate the stenosis by super heating and vaporizing the
deposited plaque. Atherectomy is yet another method of treating a
stenosed body vessel in which cutting blades are rotated to shave
the deposited plaque from the arterial wall. A vacuum catheter is
usually used to capture the shaved plaque or thrombus from the
blood stream during this procedure.
[0004] In the procedures of the kind referenced above, abrupt
reclosure may occur or restenosis of the artery may develop over
time, which may require another angioplasty procedure, a surgical
bypass operation, or some other method of repairing or
strengthening the area. To reduce the likelihood of the occurrence
of abrupt reclosure and to strengthen the area, a physician can
implant an intravascular prosthesis for maintaining vascular
patency, commonly known as a stent, inside the artery across the
lesion. The stent can be crimped tightly onto the balloon portion
of the catheter and transported in its delivery diameter through
the patient's vasculature. At the deployment site, the stent is
expanded to a larger diameter, often by inflating the balloon
portion of the catheter.
[0005] The above non-surgical interventional procedures, when
successful, avoid the necessity of major surgical operations.
However, there is one common problem which can become associated
with all of these non-surgical procedures, namely, the potential
release of embolic debris into the bloodstream that can occlude
distal vasculature and cause significant health problems to the
patient. For example, during deployment of a stent, it is possible
that the metal struts of the stent can cut into the stenosis and
shear off pieces of plaque that can travel downstream and lodge
somewhere in the patient's vascular system. Pieces of plaque
material are sometimes generated during a balloon angioplasty
procedure and become released into the bloodstream. Additionally,
while complete vaporization of plaque is the intended goal during
laser angioplasty, sometimes particles are not fully vaporized and
enter the bloodstream. Likewise, not all of the emboli created
during an atherectomy procedure may be drawn into the vacuum
catheter and, as a result, enter the bloodstream as well.
[0006] When any of the above-described procedures are performed in
the carotid arteries, the release of emboli into the circulatory
system can be extremely dangerous and sometimes fatal to the
patient. Debris carried by the bloodstream to distal vessels of the
brain can cause cerebral vessels to occlude, resulting in a stroke,
and in some cases, death. Therefore, although cerebral percutaneous
transluminal angioplasty has been performed in the past, the number
of procedures performed has been somewhat limited due to the
justifiable fear of an embolic stroke occuring should embolic
debris enter the bloodstream and block vital downstream blood
passages.
[0007] Medical devices have been developed to attempt to deal with
the problem created when debris or fragments enter the circulatory
system following vessel treatment utilizing any one of the
above-identified procedures. One approach which has been attempted
is the cutting of any debris into minute sizes which pose little
chance of becoming occluded in major vessels within the patient's
vasculature. However, it is often difficult to control the size of
the fragments which are formed, and the potential risk of vessel
occlusion still exists, making such a procedure in the carotid
arteries a high-risk proposition.
[0008] Other techniques include the use of catheters with a vacuum
source which provides temporary suction to remove embolic debris
from the bloodstream. However, as mentioned above, there can be
complications associated with such systems if the vacuum catheter
does not remove all of the embolic material from the bloodstream.
Also, a powerful suction could cause trauma to the patient's
vasculature.
[0009] Another technique which has had some success utilizes a
filter or trap downstream from the treatment site to capture
embolic debris before it reaches the smaller blood vessels
downstream. The placement of a filter in the patient's vasculature
during treatment of the vascular lesion can reduce the presence of
the embolic debris in the bloodstream. Such embolic filters are
usually delivered in a collapsed position through the patient's
vasculature and then expanded to trap the embolic debris. Some of
these embolic filters are self expanding and utilize a restraining
sheath which maintains the expandable filter in a collapsed
position until it is ready to be expanded within the patient's
vasculature. The physician can retract the proximal end of the
restraining sheath to expose the expandable filter, causing the
filter to expand at the desired location. Once the procedure is
completed, the filter can be collapsed, and the filter (with the
trapped embolic debris) can then be removed from the vessel. While
a filter can be effective in capturing embolic material, the filter
still needs to be collapsed and removed from the vessel. During
this step, there is a possibility that trapped embolic debris can
backflow through the inlet opening of the filter and enter the
bloodstream as the filtering system is being collapsed and removed
from the patient. Therefore, it is important that any captured
embolic debris remain trapped within this filter so that particles
are not released back into the body vessel.
[0010] Some prior art expandable filters vessel are attached to the
distal end of a guide wire or guide wire-like member which allows
the filtering device to be steered in the patient's vasculature as
the guide wire is positioned by the physician. Once the guide wire
is in proper position in the vasculature, the embolic filter can be
deployed to capture embolic debris. The guide wire can then be used
by the physician to deliver interventional devices, such as a
balloon angioplasty dilatation catheter or a stent delivery
catheter, to perform the interventional procedure in the area of
treatment. After the procedure is completed, a recovery sheath can
be delivered over the guide wire using over-the-wire techniques to
collapse the expanded filter for removal from the patient's
vasculature.
[0011] When a combination of an expandable filter and guide wire is
utilized, it is important that the expandable filter portion
remains flexible in order to negotiate the often tortuous anatomy
through which it is being delivered. An expandable filter which is
too stiff could prevent the device from reaching the desired
deployment position within the patient's vasculature. As a result,
there is a need to increase the flexibility of the expandable
filter without compromising its structural integrity once in
position within the patient's body vessel. Also, while it is
beneficial if the area of treatment is located in a substantially
straight portion of the patient's vasculature, sometimes the area
of treatment is at a curved portion of the body vessel which can be
problematic to the physician when implanting the expandable filter.
If the expandable filter portion is too stiff, it is possible that
the filter may not fully deploy within the curved portion of the
body vessel. As a result, gaps between the filter and vessel wall
can be formed which may permit some embolic debris to pass
therethrough. Therefore, the filtering device should be
sufficiently flexible to be deployed in, and to conform to, a
tortuous section of the patient's vasculature, when needed.
[0012] Expandable filters can be provided with some increased
flexibility by forming the struts of the filter assembly from
relatively thin material. However, the use of thin material often
can reduce the radiopacity of the expandable filter, often making
it difficult for the physician to see the filter under fluoroscopy
during deployment. Conversely, the use of thicker materials, which
can promote radiopacity of the expandable filter, usually reduces
its flexibility, which may impair the deliverability of the
expandable filter within the patient.
[0013] What has been needed is an expandable filter assembly having
high flexibility and bendability with sufficient strength and
radiopacity to be successfully deployed within a patient's
vasculature to collect embolic debris which may be released into
the patient's vasculature.
SUMMARY OF THE INVENTION
[0014] The present invention provides a highly flexible cage (also
referred to as a "basket") for use with an embolic filtering device
designed to capture embolic debris created during the performance
of a therapeutic interventional procedure, such as a balloon
angioplasty or stenting procedure, in a body vessel. The present
invention provides the physician with an embolic filtering device
having high flexibility to be steered through tortuous anatomy, but
yet possessing sufficient strength to hold open a filtering element
against the wall of the body vessel for capturing embolic debris.
An embolic filtering device made in accordance with the present
invention is relatively easy to deploy, has good visibility under
fluoroscopy, and has good flexibility and is conformable to the
patient's anatomy.
[0015] An expandable cage made in accordance with the present
invention from a self-expanding material, for example, nickel
titanium (NiTi) or spring steel, and includes a number of outwardly
extending struts capable of expanding from a collapsed position
having a first delivery diameter to an expanded or deployed
position having a second implanted diameter. A filter element made
from an embolic-capturing material is attached to the expandable
cage to move between a collapsed position and a deployed
position.
[0016] The struts of the cage can be set to remain in the expanded,
deployed position until an external force is placed over the struts
to collapse and move the struts to the collapsed position. One way
of accomplishing this is through the use of a restraining sheath,
for example, which can be placed over the filtering device in a
coaxial fashion to contact the cage and move the cage into the
collapsed position. The embolic filtering device can be placed in
the patient's vasculature and remain there for a period of time.
The filtering device can be attached to the distal end of an
elongated member, such as a guide wire, for temporary placement in
the vasculature to capture emboli created during an interventional
procedure. A guide wire may be used in conjunction with the
filtering device when embolic debris is to be filtered during an
interventional procedure. In this manner, the guide wire and
filtering assembly, with the restraining sheath placed over the
filter assembly, can be placed into the patient's vasculature. Once
the physician properly manipulates the guide wire into the target
area, the restraining sheath can be retracted to deploy the basket
into the expanded position. This can be easily performed by the
physician by simply retracting the proximal end of the restraining
sheath (located outside of the patient). Once the restraining
sheath is retracted, the self-expanding properties of the cage
cause each strut to move in a outward, radial fashion away from the
guide wire to contact the wall of the body vessel. As the struts
expand radially, so does the filter element which will now be
maintained in place to collect embolic debris that may be released
into the bloodstream as the physician performs the interventional
procedure. The guide wire can then be used by the physician to
deliver the necessary interventional device into the area of
treatment. The deployed filter element captures embolic debris
created and released into the body vessel during the interventional
procedure.
[0017] In one aspect of the present invention, the enhanced
flexibility and bendability of the embolic filtering device is
achieved through the utilization of a unique cage design having a
highly flexible and conformable circumferential member which is
adapted to expand and conform to the size and shape of the body
vessel. The expandable cage further includes at least one proximal
strut having an end connected to a guide wire and the other end
attached to the circumferential member. At least one distal strut
is attached to the circumferential member and has its other end
attached to the guide wire. The filter element is attached to the
circumferential member and will open and close as the expandable
cage moves between its expanded, deployed position and its
unexpanded, delivery position. The circumferential member is
self-expanding and is made from a highly flexible material which
allows it to conform to the particular size and shape of the body
vessel. This high flexibility and conformability of the
circumferential member allows it to deployed in curved sections of
the patient's anatomy and other eccentric vessel locations having
non-circular shaped lumens. This allows an embolic filtering device
made in accordance with the present invention to be deployed in
locations in the patient's anatomy which might not be otherwise
suitable for stiffer filtering devices. Moreover, due to the high
flexibility and conformability of the circumferential member, an
embolic filtering device made in accordance with present invention
is less likely to create gaps between the filtering element and the
wall of the vessel once deployed in the lumen. Therefore, the
potential release of embolic debris past the deployed filter can be
reduced.
[0018] In another aspect of the present invention, bending regions
formed on the circumferential member help to actuate the
circumferential member between its unexpanded and expanded
positions. In one aspect of the present invention, these bending
regions are substantially U-shaped bends formed on the
circumferential member at various locations along the member. While
the circumferential member itself is self-expanding and capable of
moving between these positions, the bending regions further enhance
the actuation of the circumferential member between these
positions. In one particular aspect of the present invention, the
proximal strut is attached directly to this bending region.
Likewise, a distal strut can be attached to a second bend section.
In this fashion, a highly bendable and conformable cage can be
produced which should conform to the particular shape of the body
vessel once deployed.
[0019] In other aspects of the present invention, a pair of
circumferential members can be utilized to create the expandable
cage which maintains a high degree of bendability and
conformability, but yet is sufficiently rigid enough to maintain
the filtering element in an expanded position once the filtering
device is fully deployed. Still other aspects of the present
invention utilize a pair of proximal struts and a pair of distal
struts to form a larger expandable cage which still retains good
bendability and conformability, yet possesses sufficiently radial
strength when deployed to maintain proper wall apposition between
the filter element and the body vessel.
[0020] It is to be understood that the present invention is not
limited by the embodiments described herein. The present invention
can be used in arteries, veins, and other body vessels. Other
features and advantages of the present invention will become more
apparent from the following detailed description of the invention,
when taken in conjunction with the accompanying exemplary
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a perspective view of an embolic filtering device
embodying features of the present invention.
[0022] FIG. 2 is a perspective view of the expandable cage which
forms part of the embolic filtering device of FIG. 1.
[0023] FIG. 3 is an elevational view, partially in cross section,
of an embolic filtering device embodying features of the present
invention as it is being delivered within a body vessel downstream
from an area to be treated.
[0024] FIG. 4 is an elevational view, partially in cross section,
similar to that shown in FIG. 3, wherein the embolic filtering
device is deployed in its expanded position within the body
vessel.
[0025] FIG. 5 is a perspective view of an alternative embodiment of
an expandable cage similar to the cage of FIG. 2 which is attached
to a guide wire that extends through the expandable cage to the
distal end of the cage.
[0026] FIG. 6 is another particular embodiment of an embolic
filtering device embodying features of the present invention.
[0027] FIG. 7 is an side elevational view of the expandable cage
which forms part of the embolic filtering device shown in FIG.
6.
[0028] FIG. 8 is a top plan view of the expandable cage of FIG. 7
taken along line 8-8.
[0029] FIG. 9 is an end view of the expandable cage of FIG. 7 taken
along line 9-9.
[0030] FIG. 10 is an alternative embodiment of an embolic filtering
device embodying features of the present invention which utilizes a
similar expandable cage as shown in FIG. 5.
[0031] FIG. 11 is an elevational view, partially in cross-section,
of the distal end of the embolic filtering device of FIG. 1.
[0032] FIG. 12 is an elevational view, partially in cross-section,
of the distal end of the embolic filtering device of FIG. 10.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] Turning now to the drawings, in which like reference
numerals represent like or corresponding elements in the drawings,
FIGS. 1 and 2 illustrate one particular embodiment of an embolic
filtering device 20 incorporating features of the present
invention. This embolic filtering device 20 is designed to capture
embolic debris which may be created and released into a body vessel
during an interventional procedure. The embolic filtering device 20
includes an expandable filter assembly 22 having a self-expanding
basket or cage 24 and a filter element 26 attached thereto. In this
particular embodiment, the expandable filter assembly 22 is
rotatably mounted on the distal end of an elongated (solid or
hollow) cylindrical tubular shaft, such as a guide wire 28. The
guide wire has a proximal end (not shown) which extends outside the
patient and is manipulated by the physician to deliver the filter
assembly into the target area in the patient's vasculature. A
restraining or delivery sheath 30 (FIG. 3) extends coaxially along
the guide wire 28 in order to maintain the expandable filter
assembly 22 in its collapsed position until it is ready to be
deployed within the patient's vasculature. The expandable filter
assembly 22 is deployed by the physician by simply retracting the
restraining sheath 30 proximally to expose the expandable filter
assembly. Once the restraining sheath is retracted, the
self-expanding cage 24 immediately begins to expand within the body
vessel (see FIG. 4), causing the filter element 26 to expand as
well.
[0034] An obturator 32 affixed to the distal end of the filter
assembly 32 can be implemented to prevent possible "snowplowing" of
the embolic filtering device as it is being delivered through the
vasculature. The obturator can be made from a soft polymeric
material, such as Pebax 40D, and has a smooth surface to help the
embolic filtering device travel through the vasculature and cross
lesions while preventing the distal end of the restraining sheath
30 from "digging" or "snowplowing" into the wall of the body
vessel.
[0035] In FIGS. 3 and 4, the embolic filtering device 20 is shown
as it is being delivered within an artery 34 or other body vessel
of the patient. Since the embolic filtering device made in
accordance with the present invention possesses excellent
bendability and flexibility, it will conform well to the shape of
the vasculature while allowing the filter assembly to more easily
negotiate a curved radius in the patient's vasculature.
[0036] Referring now to FIG. 4, the embolic filtering device 22 is
shown in its expanded position within the patient's artery 34. This
portion of the artery 34 has an area of treatment 36 in which
atherosclerotic plaque 38 has built up against the inside wall 40
of the artery 34. The filter assembly 22 is to be placed distal to,
and downstream from, the area of treatment 36. For example, the
therapeutic interventional procedure may comprise the implantation
of a stent (not shown) to increase the diameter of an occluded
artery and increase the flow of blood therethrough. It should be
appreciated that the embodiments of the embolic filtering device
described herein are illustrated and described by way of example
only and not by way of limitation. Also, while the present
invention is described in detail as applied to an artery of the
patient, those skilled in the art will appreciate that it can also
be used in other body vessels, such as the coronary arteries,
carotid arteries, renal arteries, saphenous vein grafts and other
peripheral arteries. Additionally, the present invention can be
utilized when a physician performs any one of a number of
interventional procedures, such as balloon angioplasty, laser
angioplasty or atherectomy which generally require an embolic
filtering device to capture embolic debris created during the
procedure.
[0037] The cage 24 includes self-expanding struts which, upon
release from the restraining sheath 30, expand the filter element
26 into its deployed position within the artery (FIG. 4). Embolic
particles 27 created during the interventional procedure and
released into the bloodstream are captured within the deployed
filter element 26. The filter may include perfusion openings 29, or
other suitable perfusion means, for allowing blood flow through the
filter 26. The filter element will capture embolic particles which
are larger than the perfusion openings while allowing some blood to
perfuse downstream to vital organs. Although not shown, a balloon
angioplasty catheter can be initially introduced within the
patient's vasculature in a conventional SELDINGER technique through
a guiding catheter (not shown). The guide wire 28 is disposed
through the area of treatment and the dilatation catheter can be
advanced over the guide wire 28 within the artery 34 until the
balloon portion is directly in the area of treatment 36. The
balloon of the dilatation catheter can be expanded, expanding the
plaque 38 against the wall 40 of the artery 34 to expand the artery
and reduce the blockage in the vessel at the position of the plaque
38. After the dilatation catheter is removed from the patient's
vasculature, a stent (not shown) could be implanted in the area of
treatment 36 using over-the-wire techniques to help hold and
maintain this portion of the artery 34 and help prevent restenosis
from occurring in the area of treatment. The stent could be
delivered to the area of treatment on a stent delivery catheter
(not shown) which is advanced from the proximal end of the guide
wire to the area of treatment. Any embolic debris created during
the interventional procedure will be released into the bloodstream
and should enter the filter 26. Once the procedure is completed,
the interventional device may be removed from the guide wire. The
filter assembly 22 can also be collapsed and removed from the
artery 34, taking with it any embolic debris trapped within the
filter element 26. A recovery sheath (not shown) can be delivered
over the guide wire 28 to collapse the filter assembly 22 for
removal from the patient's vasculature.
[0038] Referring again to FIGS. 1 and 2, the expandable cage 24
includes a pair of self-expanding proximal struts 42 and 44 which
help to deploy the filter element 26 and the remainder of the
expandable cage. These proximal struts 42 and 44 are coupled to a
first circumferential member 46 which is adapted to move from the
unexpanded delivery position (FIG. 3) to the expanded deployed
position (FIG. 4). A second circumferential member 48 is, in turn,
coupled to the first circumferential member 46. The deployment of
the first and second circumferential members 46 and 48 results in
the filter element 26 being placed against the wall 40 of the
artery or other body vessel, even if the lumen of the body vessel
is non-circular. A pair of distal struts 50 and 52 connected to the
second circumferential member 48 extend distally towards the
obturator 32. The first and second circumferential members 46 and
48 are coupled to, and spaced apart, from each other by short
connecting struts 54. It should be appreciated that a single
circumferential member could be used to create an expandable cage
made in accordance with the present invention. Also, additional
circumferential members could be added to create a larger
expandable cage. Additionally, while only two proximal struts and
distal struts are shown in the cage design of FIGS. 1-5, the cage
could also be made with a single proximal and distal strut (see
FIGS. 6-10) or additional struts (not shown) could be implemented
without departing from the spirit and scope of the present
invention.
[0039] As can be seen in FIGS. 1 and 2, each circumferential member
includes four bending regions 56, 58, 60 and 62 formed on the
circumferential member to enhance the performance of the
circumferential member to bend as it moves between the unexpanded
and expanded positions. In the particular embodiment shown in FIG.
2, each bending region 56-62 is placed on the circumferential
member approximately 90 degrees apart. Each of the proximal struts
includes a first end 64 attached to the collar 65 which is
rotatably mounted to the guide wire 28. Each proximal strut
includes a second end 66 connected to one of the proximal bending
regions 56 and 58 of the first circumferential member 46. These
proximal bending regions 56 and 58 are spaced approximately 180
degrees apart from each other along a circular diameter defined by
the expanded circumferential member 46. Each of the distal struts
50 and 52, in turn, has a first end 68 connected to and extending
towards the obturator 32 and a second end 70 attached to the distal
bending regions 60 and 62 of the second circumferential member 48.
These distal bending regions 60 and 62, in turn, are spaced
approximately 180 degrees apart from each other and are offset 90
degrees from the proximal bending regions 56 and 58.
[0040] Each of the bending regions is substantially U-shaped which
help to create a natural bending point on the circumferential
member. While the flexibility of the circumferential members is
already high, these bending regions only help to increase the
ability of the circumferential member to collapse or expand when
needed. In this manner, the shape of the hinge regions creates a
natural hinge that helps to actuate the expandable cage between the
unexpanded and expanded positions. As can be best seen in FIG. 2,
the U-shaped bending regions 54 and 56 are positioned directly
opposite the U-shaped portion of the distal bending regions 58 and
60. The positioning of the direction of the U portion also enhances
the ability of the circumferential member to bend. These
circumferential members 46 and 48, while being quite bendable,
nevertheless maintain sufficient radial strength to remain in the
deployed position to hold the filter element 26 open in the body
vessel for collecting embolic particles which may be entrained in
the body fluid.
[0041] The shape of the bending regions are shown as substantially
U-shaped portions, however, any one of a number of different shapes
could also be utilized to create a natural bending point on the
circumferential member. For example, a V-shaped region could also
be formed and would function similarly to a U-shaped portion to
facilitate the collapse and expansion of the circumferential member
as needed. Alternative shapes and sizes of the bending regions also
could be utilized without departing from the spirit and scope of
the invention. Although four bending regions are shown on each
circumferential member, it should be appreciated that the number of
different bending regions could be increased or decreased as
needed. For example, it is possible to utilize only two bending
regions, as is shown in the embodiment of the expandable cage of
FIG. 6, in order to facilitate bending. Additional bending regions
also could be utilized in the event that additional proximal or
distal struts are used to form the expandable cage. Moreover,
different sizes, shapes and location of the bending regions can be
utilized on any circumferential member.
[0042] The expandable cage 24 of FIGS. 1 and 2 is shown rotatably
mounted to the distal end of the guide wire 28 to allow the entire
filtering assembly 22 to remain stationary once deployed in the
body vessel. This feature prevents the filtering assembly from
rotating in the event that the proximal end of the guide wire is
accidentally rotated by the physician during use. As a result, the
possibility that the deployed filtering assembly 22 could be
rotated to cause trauma to the wall of the vessel is minimized.
Referring specifically to FIGS. 1 and 2, the first end 64 of the
proximal struts 42 and 44 are attached to the collar 65 which is
rotatably mounted on the guide wire 28 between a pair of stop
fittings 72 and 74. The stop fittings 72 and 74 allow the
expandable cage 24 to spin on the guide wire but restricts the
longitudinal movement of the cage on the guide wire. This
particular mechanism is but one way to rotatably mount the
expandable cage 24 to the guide wire 28.
[0043] The expandable cage is shown in FIGS. 1 and 2 does not
include a segment of guide wire which would otherwise extend
through the expandable cage 24 to the distal end where the coil tip
76 extends through the obturator 32. In this manner, the
elimination of this short segment of guide wire through the
expandable cage 24 may help collapse the filter assembly 22 to a
smaller delivery profile. The lack of the guide wire segment also
may help to increase the flexibility and bendability of the
filtering assembly 22 somewhat as it is being delivered through the
patient's vasculature.
[0044] Referring now to FIG. 5, an alternative version of the
embolic filtering device 20 is shown as it is rotatably mounted
onto a guide wire 28. In FIG. 5, the filter element has been
removed to better show the portion of the guide wire which extends
through the expandable cage to the coil tip of the guide wire. In
this particular embodiment, a short segment of guide wire 78 is
present and extends through the expandable cage 24 and extends
through the obturator 32. This particular embodiment of the embolic
filtering device functions in the same fashion as the filter device
shown and described in FIGS. 1-4. However, a fill-length guide wire
is utilized in conjunction with this particular embodiment. While
this particular embodiment of the filtering device may not be
collapsed to a smaller profile as the one shown in FIGS. 1 and 2,
nevertheless it has the advantage of a fill-length guide wire which
allows the physician to manipulate the proximal end of the guide
wire in order to steer the device in the patient's vasculature. The
expandable cage 24 would be rotatably mounted on the guide wire as
the proximal collar would be placed between two stop fittings
located on the guide wire. One benefit from this particular
embodiment stems from the ability of the physician to control the
proximal end of the guide wire in order to steer the distal coil
tip 76 into the desired vessel when delivering the device through
the patient's vasculature. The embodiment of the filtering device
shown in FIG. 1, while having its own advantages, does not allow
the guide wire itself to be rotated at its proximal end of the
guide wire to steer the distal coil tip 76 of the guide wire.
However, the composite delivery sheath utilized to restrain and
maintain the expandable filter in its collapsed position during
delivery could be rotated by the physician to steer the coil tip
into the desired vessel. In this manner, the proximal end of the
delivery sheath could be torqued by the physician to rotate the
distal coil wire into the target location. Alternatively, the
particular design shown in FIG. 1 could also be modified so that
the distal end of the guide wire, rather than being rotatably
connected to the cage 24, is permanently attached together. In such
a modification, the first ends of the proximal struts 42 and 44
could be simply bonded or otherwise fastened directly to the guide
wire such that the expandable cage will rotate as the guide wire is
being rotated. This particular emobidment would allow the physician
to simply torque the proximal end of the guide wire to steer the
distal coil into the desired area of treatment.
[0045] Referring now to FIG. 11, one manner in which the distal
ends 68 of the distal struts 52 and 50 could be attached to the
obturator 32 as shown. As can be seen in FIG. 11, the distal ends
68 are attached to a tubular member 80 which extends into the
obturator 32. The ends 68 are attached to the outer surface 82 of
the tubular member 80. The filter 26 tapers to a distal end 84
which is, in turn, bonded or otherwise adhesively attached to the
outer surface 82 of this tubular member 80. Likewise, at least a
portion of the tubular member 80 is in contact with the obturator
32 and is adhesively bonded or otherwise affixed thereto. The inner
surface 86 of the tubular member 80 is in turn attached to a short
segment 88 of the guide wire which extends out to the distal coil
tip 76. In this manner, the short segment 88 of the guide wire is
adhesively bonded or otherwise attached to the inner surface 68 to
remain in place. The combination of elements thus form an integral
distal end for the filtering assembly which will remain intact
during usage.
[0046] Referring now to FIGS. 6-9, an alternative embodiment of the
embolic filter device 90 is shown which includes an expandable
filter assembly 92 with an expandable cage 94. In this particular
embodiment, the expandable cage is a modification of the expandable
cage 24 shown in FIGS. 1-5. The filter assembly 92 includes the
filter member 96 which is utilized to filter the embolic debris in
the body vessel and includes a plurality of openings 98 through
which the body fluid flows through while the embolic particles
remain trapped in the pocket formed by the filter member 96. The
filter assembly 92 is also shown attached to a guide wire 100 which
has a proximal end (not shown) which extends outside of the
patient's body and is manipulated by the physician in order to
steer the device into the target area in the patient's vasculature.
This particular embodiment 90 is self-expanding, as the other
embodiment shown in FIGS. 1-5, and would be kept in a collapsed
delivery position through the use of a sheath which would extend
over the filter assembly (as is shown in FIG. 3) in order to
deliver the device into the target area.
[0047] The expandable cage 94 includes a pair of circumferential
members 102 and 104 which are connected together by connecting
struts 106. This particular embodiment utilizes a single proximal
strut 108 and a single distal strut which extends from the second
circumferential member 104 to the obturator 112. A distal coil tip
114 extends distally from the obturator 112 and is utilized by the
physician to steer the device into the desired body lumen.
[0048] The circumferential members 102 and 104 of this particular
expandable cage 94 includes only a pair of bending regions 114 and
116 although it is still possible to utilize other bending regions
along the circumferential member if desired. As a result, the use
of a single proximal strut 108 minimizes the surface area of struts
placed in front of the opening of the filter assembly 92 thus
minimizing the chances that emboli could collect on strut areas
rather than being forced into the filter member 96. The use of a
single distal strut also allows the device to be more flexible in
the distal area where flexibility is needed when negotiating
tortuous anatomy. It should be appreciated that a single
circumferential member could be used in accordance with the present
embodiment or additional circumferential members could be utilized
to create a longer filtering assembly if desired.
[0049] The proximal strut 108 includes one end 118 which is
attached to a collar 120 that is rotatably mounted onto the distal
end of the guide wire 100. A pair of stop fittings 122 and 124
maintain the collar 120 rotatably mounted to the distal end of the
guide wire 100. The other end 126 of the proximal strut 108 is in
turn attached to the bending region 114 located on the proximal
circumferential member 102. The distal strut 110 includes one end
128 which is attached to the bending region 116 of the second
circumferential member 104 with the other end 130 attached to the
obturator 112. FIG. 12 shows one particular method for attaching
the distal end 130 to the obturator 112. The method of attachment
is very similar to the attachment arrangement shown in FIG. 11 in
that the distal end 130 is attached to a tubular member 132 having
an outside surface 134 and an inner surface 136. A short segment
138 of the guide wire which is attached to the distal coil tip 114
can be adhesively secured or otherwise fastened to the inner
surface 136 of the tubular member 132. Likewise, the distal end 130
of the strut 110 is adhesively bonded or otherwise secured to the
outer surface 134 of the tubular member 132. The filter member 96
terminates at a distal end 140 which can be bonded both to the
outer surface 134 of the tubular member 132 and also to the inner
surface of the obturator 112. In this manner, the distal end of the
assembly will remain securedly fastened to form an integral unit
that will remain intact during usage.
[0050] Referring now to FIG. 10, an alternative design to the
embodiment of FIGS. 6-9 is shown in which a short segment 142 of
the guide wire extends through the opening of the expandable cage
94 and extends to the distal end where the distal coil tip 114 is
located. In this particular embodiment of the embolic filtering
device 90, the short segment 142 of the guide wire extends through
the expandable cage 94 and performs substantially the same
functions as the embodiment shown in FIG. 5. The tubular member 132
(not shown in FIG. 10) can also extend into the expandable cage 94
to help prevent the filter 96 from tangling on the guide wire
segment 142 when the cage 94 is collapsed. The use of a guide wire
which extends to the distal most end of the device provides good
torqueability to the physician when maneuvering the device in the
patient's vasculature. It should also be noted that the expandable
cage 94 shown in FIGS. 6-9 could also be permanently affixed to the
distal end of the guide wire, rather than being rotatably mounted
thereto.
[0051] The expandable cage of the present invention can be made in
many ways. One particular method of making the cage is to cut a
thin-walled tubular member, such as nickel-titanium hypotube, to
remove portions of the tubing in the desired pattern for each
strut, leaving relatively untouched the portions of the tubing
which are to form each strut. The tubing may be cut into the
desired pattern by means of a machine-controlled laser. The tubing
used to make the cage could possible be made of suitable
biocompatible material such as spring steel. Elgiloy is another
material which could possibly be used to manufacture the cage.
Also, very elastic polymers possibly could be used to manufacture
the cage.
[0052] The strut size is often very small, so the tubing from which
the cage is made may have a small diameter. Typically, the tubing
has an outer diameter on the order of about 0.020-0.040 inches in
the unexpanded condition. Also, the cage can be cut from large
diameter tubing. Fittings are attached to both ends of the lased
tube to form the final cage geometry. The wall thickness of the
tubing is usually about 0.076 mm (0.001-0.006 inches). As can be
appreciated, the strut width and/or depth at the bending points
will be less. For cages deployed in body lumens, such as PTA
applications, the dimensions of the tubing may be correspondingly
larger. While it is preferred that the cage be made from laser cut
tubing, those skilled in the art will realize that the cage can be
laser cut from a flat sheet and then rolled up in a cylindrical
configuration with the longitudinal edges welded to form a
cylindrical member.
[0053] Generally, the tubing is put in a rotatable collet fixture
of a machine-controlled apparatus for positioning the tubing
relative to a laser. According to machine-encoded instructions, the
tubing is then rotated and moved longitudinally relative to the
laser which is also machine-controlled. The laser selectively
removes the material from the tubing by ablation and a pattern is
cut into the tube. The tube is therefore cut into the discrete
pattern of the finished struts. The cage can be laser cut much like
a stent is laser cut. Details on how the tubing can be cut by a
laser are found in U.S. Pat. Nos. 5,759,192 (Saunders), 5,780,807
(Saunders) and 6,131,266 (Saunders) which have been assigned to
Advanced Cardiovascular Systems, Inc.
[0054] The process of cutting a pattern for the strut assembly into
the tubing generally is automated except for loading and unloading
the length of tubing. For example, a pattern can be cut in tubing
using a CNC-opposing collet fixture for axial rotation of the
length of tubing, in conjunction with CNC X/Y table to move the
length of tubing axially relative to a machine-controlled laser as
described. The entire space between collets can be patterned using
the CO.sub.2 or Nd:YAG laser set-up. The program for control of the
apparatus is dependent on the particular configuration used and the
pattern to be ablated in the coding.
[0055] A suitable composition of nickel-titanium which can be used
to manufacture the strut assembly of the present invention is
approximately 55% nickel and 45% titanium (by weight) with trace
amounts of other elements making up about 0.5% of the composition.
The austenite transformation temperature is between about 0.degree.
C. and 20.degree. C. in order to achieve superelasticity at human
body temperature. The austenite temperature is measured by the bend
and free recovery tangent method. The upper plateau strength is
about a minimum of 60,000 psi with an ultimate tensile strength of
a minimum of about 155,000 psi. The permanent set (after applying
8% strain and unloading), is less than approximately 0.5%. The
breaking elongation is a minimum of 10%. It should be appreciated
that other compositions of nickel-titanium can be utilized, as can
other self-expanding alloys, to obtain the same features of a
self-expanding cage made in accordance with the present
invention.
[0056] In one example, the cage of the present invention can be
laser cut from a tube of nickel-titanium (Nitinol) whose
transformation temperature is below body temperature. After the
strut pattern is cut into the hypotube, the tubing is expanded and
heat treated to be stable at the desired final diameter. The heat
treatment also controls the transformation temperature of the cage
such that it is super elastic at body temperature. The
transformation temperature is at or below body temperature so that
the cage is superelastic at body temperature. The cage is usually
implanted into the target vessel which is smaller than the diameter
of the cage in the expanded position so that the struts of the cage
apply a force to the vessel wall to maintain the cage in its
expanded position. It should be appreciated that the cage can be
made from either superelastic, stress-induced martensite NiTi or
shape-memory NiTi.
[0057] The cage could also be manufactured by laser cutting a large
diameter tubing of nickel-titanium which would create the cage in
its expanded position. Thereafter, the formed cage could be placed
in its unexpanded position by backloading the cage into a
restraining sheath which will keep the device in the unexpanded
position until it is ready for use. If the cage is formed in this
manner, there would be no need to heat treat the tubing to achieve
the final desired diameter.
[0058] This process of forming the cage could be implemented when
using superelastic or linear-elastic nickel-titanium.
[0059] The struts forming the proximal struts can be made from the
same or a different material than the distal struts. In this
manner, more or less flexibility for the proximal struts can be
obtained. When a different material is utilized for the struts of
the proximal struts, the distal struts can be manufactured through
the lazing process described above with the proximal struts being
formed separately and attached. Suitable fastening means such as
adhesive bonding, brazing, soldering, welding and the like can be
utilized in order to connect the struts to the distal assembly.
Suitable materials for the struts include superelastic materials,
such as nickel-titanium, spring steel, Elgiloy, along with
polymeric materials which are sufficiently flexible and
bendable.
[0060] The connecting struts utilized to connect one or more
circumferential members together are shown generally as straight
segments. However, it is possible to utilize non-linear shapes and
sizes which may provide additional flexibility and bendability
within the patient's anatomy. Additionally, it is possible to make
these connecting struts out of materials which are different from
the rest of the expandable cage to further increase flexibility if
needed. For example, the connecting strut could be made in an
S-shape which may provide additional flexibility in certain curved
locations in the patient's anatomy. Moreover, the size and width of
the strut could be varied from the remaining strut widths and
thicknesses in order to promote additional flexibility. In a
similar fashion, the bending regions formed on the circumferential
members could also be formed with thinner and narrower strut widths
than the remaining elements of the cage in order to enhance
flexibility at these bending regions.
[0061] The polymeric material which can be utilized to create the
filtering element include, but is not limited to, polyurethane and
Gortex, a commercially available material. Other possible suitable
materials include ePTFE. The material can be elastic or
non-elastic. The wall thickness of the filtering element can be
about 0.00050-0.0050 inches. The wall thickness may vary depending
on the particular material selected. The material can be made into
a cone or similarly sized shape utilizing blow-mold technology or
dip technology. The openings can be any different shape or size. A
laser, a heated rod or other process can be utilized to create to
perfusion openings in the filter material. The holes, would of
course be properly sized to catch the particular size of embolic
debris of interest. Holes can be lazed in a spinal pattern with
some similar pattern which will aid in the re-wrapping of the media
during closure of the device. Additionally, the filter material can
have a "set" put in it much like the "set" used in dilatation
balloons to make the filter element rewrap more easily when placed
in the collapsed position.
[0062] The materials which can be utilized for the restraining
sheath can be made from polymeric material such as cross-linked
HDPE. This sheath can alternatively be made from a material such as
polyolifin which has sufficient strength to hold the compressed
strut assembly and has relatively low frictional characteristics to
minimize any friction between the filtering assembly and the
sheath. Friction can be further reduced by applying a coat of
silicone lubricant, such as Microglide.RTM., to the inside surface
of the restraining sheath before the sheaths are placed over the
filtering assembly.
[0063] Further modifications and improvements may additionally be
made to the device and method disclosed herein without departing
from the scope of the present invention. Accordingly, it is not
intended that the invention be limited, except as by the appended
claims.
* * * * *